I've had good success with the ASRock X470D4U and X570D4U server boards that accept AMD Ryzen CPUs and have ECC support. Just make sure to use the dedicated IP

I've had good success with the ASRock X470D4U and X570D4U server boards that accept AMD Ryzen CPUs and have ECC support. Just make sure to use the dedicated IPMI ethernet port rather than the shared ethernet port. The shared ethernet port has the nasty downside of losing connectivity during reboot while the dedicated port does not. Note that if you choose the xx00G series of CPUs with integrated GPUs, only support ECC in the Pro models. The xxx0G CPUs have quite good performance in much lower power budgets, hence why they're worth mentioning I've built more than 5 servers with these boards to good success.